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High suction , normal head pressure

Discussion in 'Residential' started by Randysmit1986, Jun 3, 2017.

  1. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,282
    Location:
    Denison TX

    Dude theres only two possibilities that i know of
    1: high cfm. My unit runs high suction pressure because its moving 450 cfm per ton

    2: wore vanes in the compressor. Try pumping it down and see if it will pull down and hold. If the vanes are wore you will have high suction
     
    Randysmit1986 likes this.
  2. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,282
    Location:
    Denison TX
    Wait, is this an attic install? Is the ahu sucking in a shitload of hot air in the attic for some reason?


    Are the pressurss pulsing? Like non condensables?
     
  3. Randysmit1986

    Randysmit1986 New Member

    Messages:
    24
     
  4. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,282
    Location:
    Denison TX
    Gotcha. Well its either gotta be high load or a defective compressor.

    I forget what company you said it was but we have to clear that stuff with tech support. They are gonna want cfm measurements, total static pressures. Temps across the coil, not just supply and return. Amp draws.....the works.
     
  5. Randysmit1986

    Randysmit1986 New Member

    Messages:
    24
    Ameristar..cheap trane
     
  6. 4x4Freak

    4x4Freak New Member

    Messages:
    826
    Location:
    Kermit, TX
    This ^

    You have high suction (about 35 psi) & low head (about 50 psi). SH is high so txv is not over feading. SC is low so txv isn't closed off. This is assuming charge is correct or close. You did weigh it in right?

    I doubt the airflow is too far out unless the system is severely mismatched.

    Is there any way it could be pulling in hot air? Is there any return duct in the attic? Were your return temps taken at the furnace or the return grill?

    Assuming there's nothing out of the ordinary going on, it all leads to a weak compressor. Of course it can be eliminated or verified very simply by doing a pump down test like has been suggested several times.

    Zach
     
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  7. Randysmit1986

    Randysmit1986 New Member

    Messages:
    24
    Return temps checked at furnace. Charge was weighed in line set is about 15ft. I wish it didn't start raining as I also would have checked discharge line to make sure it was creating heat
     
  8. Anita sannich

    Anita sannich sugar and spice and all that sh#t

    Messages:
    415
    Location:
    Spokane WA
    Is the filter drier backwards?
     
  9. pintofstout

    pintofstout New Member

    Messages:
    1,461
    Location:
    Olean, NY
    I'm assuming you've confirmed by now that the evap is NOT too large....

    Look at all this speculation. We all want closure so bad....



    Sent from my iPhone using Tapatalk
     
  10. tuna

    tuna New Member

    Messages:
    2,849
    My thoughts would be expansion device stuck open. Doesn't seem like you would have superheat with this problem, but that's my guess.
     
    Randysmit1986 likes this.
  11. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,282
    Location:
    Denison TX
    Well so far he hasnt checked anything so we will see. Maybe hes gonna let it ride
     
    Randysmit1986 likes this.
  12. Randysmit1986

    Randysmit1986 New Member

    Messages:
    24
    The joker didn't install one smh
     
  13. Randysmit1986

    Randysmit1986 New Member

    Messages:
    24
    I advised homeowner to try and get the installing company out because the work should be under warranty. Trying to help her before she has to pay for my labor
     
  14. Anita sannich

    Anita sannich sugar and spice and all that sh#t

    Messages:
    415
    Location:
    Spokane WA
    Only the good die young, except compressors..
     
  15. tuna

    tuna New Member

    Messages:
    2,849
    Just wondering how to troubleshoot this. :headscratch:I think I'd slowly close the liquid service valve making it the metering device. See if that made the pressures more normal. This would determine if the exp valve was stuck open.
     
    Randysmit1986 likes this.
  16. pintofstout

    pintofstout New Member

    Messages:
    1,461
    Location:
    Olean, NY
    You could just play with the bulb, make it starve and flood.
    Blocking the LL might cost the x valve it's 100 lb diff and make the x throw in a monkey wrench, i would think.

    I think you've gotta start with pump down test. I think that compressor has blow by


    Sent from my iPhone using Tapatalk
     
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  17. pintofstout

    pintofstout New Member

    Messages:
    1,461
    Location:
    Olean, NY
    The wild card for me is the fact that it's still under charged. What would happen with a solid column of liquid at the x valve. Maybe then we wouldn't have superheat anymore, then i would change my tune on the low compression

    In my experience 3 degrees of subcooling equals zero subcooling.


    Sent from my iPhone using Tapatalk
     
    Randysmit1986 likes this.